An integrated gas spectroscopy system -- combining TeraFETs and THz QCLs to enable 2--5-THz power detection and heterodyne mixing

我们银河系中大约一半的光位于太赫兹（THz）或光谱的远红外部分（0.3-10 THz，30-1000微米波长），但使用现有的卫星仪器无法检测到。 解开这部分光谱将揭示驱动恒星和行星形成的过程，并将填补我们对地球大气中气候变化化学的理解的重要空白。尽管有着巨大的潜力，但太赫兹系统通常过于庞大，脆弱和复杂，无法在实验室外使用。 一个关键的限制是质量好的THz探测器的可用性，因为现有的设备要么在更高的THz频率下灵敏度差，要么需要极端的冷却，要么太慢而无法研究发生的化学反应。 在该计划中，我们将通过开发第一个紧凑，灵敏和快速的THz探测器系统来克服这些问题，该系统适用于痕量气体探测和与卫星有效载荷集成。这些将基于“TeraFET”器件，先进的场效应晶体管结构，与THz天线集成。在过去的几年里，它们已经成为整个THz光谱范围内强大的辐射探测器。它们可以完全在主流微电子技术的代工厂制造，具有许多随之而来的好处，例如高性能的再现性和构建检测器阵列的可能性。TeraFET器件将被设计为精确检测频率约为2.0、3.5和4.7 THz的辐射，对应于重要气体种类的“指纹”（例如，O、OH、CO、NO和HO 2），这是观测深空和地球高层大气化学过程的关键。我们将使用特制的THz量子级联激光（THz QCL）源对这些新设备的灵敏度，噪声和频率响应进行详细表征-高度紧凑的THz辐射源，产生的功率是任何类似尺寸设备的1000倍。 TeraFET将作为THz辐射的直接探测器，也将作为未来在卫星接收器系统中使用的混频器。我们将开发第一个包含QCL和TeraFET器件的紧凑型集成THz系统，安装在同一个热封装中，首次实现THz功率的原位目标监测和控制。 我们将展示一个专门构建的太赫兹痕量气体检测系统，并展示使用适合集成和包装的紧凑型窄带检测器首次有针对性地检测太赫兹气体指纹。

Approximately half the light in our galaxy lies in the terahertz (THz) or far-infrared part of the spectrum (0.3-10 THz, 30–1000-micron wavelength), and yet it is undetectable using existing satellite-borne instrumentation. Unlocking this part of the spectrum would reveal the processes that drive the formation of stars and planets and would fill important gaps in our understanding of the chemistry of climate change in the Earth’s atmosphere.Despite this great potential, THz systems are generally too large, fragile, and complex for use outside the laboratory. A key limitation is the availability of good quality THz detectors, as existing devices either have poor sensitivity at higher THz frequencies, require extreme cooling, or are too slow to study chemical reactions as they happen. In this programme, we will overcome these issues by developing the first compact, sensitive, and fast THz detector systems that are suitable for trace-gas detection and integration with satellite payloads. These will be based on “TeraFET” devices, advanced field-effect transistor structures, integrated with THz antennas. They have established themselves in the last years as powerful detectors of radiation over the entire THz spectrum. They can be fabricated entirely in foundries with the technologies of mainstream microelectronics, with many ensuing benefits such as a high performance reproducibility and the possibility to build detector arrays. TeraFET devices will be designed to detect radiation precisely at frequencies around 2.0, 3.5 and 4.7 THz, corresponding to the “fingerprints” of important gas species (e.g., O, OH, CO, NO and HO2), which are key to observing chemical processes in deep space and the Earth’s upper atmosphere. We will undertake detailed characterisation of the sensitivity, noise and frequency response of these new devices using purpose-built THz quantum-cascade laser (THz QCL) sources – highly compact sources of THz radiation, yielding >1000 times the power of any similar-sized device. TeraFETs will be established both as direct detectors of THz radiation, and also as mixers for future use in satellite-borne receiver systems. We will develop the first compact and integrated THz systems containing a QCL and TeraFET device, mounted into the same thermal packaging, enabling in situ targeted monitoring and control of THz power for the first time. We will demonstrate a purpose-built THz trace-gas detection system and demonstrate the first targeted detection of THz gas fingerprints using a compact narrowband detector suitable for integration and packaging.